DTC 44

Code 44 Chart:

Wiring Diagram For Oxygen Sensor:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volts between terminals "D6" and "D7". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). The oxygen sensor varies the voltage within a range of about 1.0 volt if the exhaust is rich, down through about 0.10 volts if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below about 315°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. A Code 44 is set when the oxygen sensor signal voltage on circuit 412:
^ Remains below 0.2 volts for 50 seconds.
^ And the system is operating in "Closed Loop".

DIAGNOSTIC AIDS:

Using the "Scan" tool, observe the block learn values at different engine speeds and air flow conditions. The "Scan" also displays the block cells, so the block learn values can be checked in each of the cells to determine when the Code 44 may have been set. If the conditions for Code 44 exists, the block learn values will be around 150.

^ Oxygen Sensor Wire - Sensor pigtail may be mispositioned and contacting the exhaust manifold.
^ Check for intermittent ground in wire between connector and sensor.
^ MAP Sensor - A Manifold Absolute Pressure (MAP) sensor output that causes the ECM to sense a higher than normal vacuum will cause the system to go lean. Disconnect the MAP sensor harness connector and if the lean condition is gone, replace the MAP sensor.
^ Fuel Contamination - Water, even in small amounts, near the in-tank fuel pump inlet, can be delivered to the injectors. The water causes a lean exhaust and can set a Code 44.
^ Fuel Pressure - System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds an/or loads to confirm. Related Tests, Information and Procedures
^ AIR System - Be sure air is not being directed to the exhaust ports while in "Closed Loop". If the block learn value goes down while squeezing air hose to left side of exhaust ports.
^ Lean injector(s).
^ If all the above checks OK, the oxygen sensor is faulty.